Dyeing of fabric



Patented June 18, 1929.

UNITED STATES PATENT OFFICE.

GEORGE FREEMAN LLOYD, 0F BRIGHTON, VICTORIA, AUSTRALIA, ASSIGNOR T0 SPEC- TRUM DYES PROPRIETARY LIMITED, OF MELBOURNE, S.

PAN Y OF VICTORIA.

C. 4, AUSTRALIA A COM- DYEING OF FABRIC.

-No Drawing. Application filed. April 6, 1928, Serial No. 268,076, and in Australia February 6, 1928.

This invention relates to the treatment of dyed fabrics and its object is to enable the colour of a dyed fabric to be transformed to a lighter colour. The word colour is used herein in its wide sense to include a shade of colour.

In the past it has been known to strip dark colours from fabrics and, after this complete removal of the colours dyed thereon, to redye the fabrics to the particular colour desired.

I have found that, instead of completely stripping the colour from the fabric, it is possible to produce selectively any one of a range of intermediate lighter colours by a controlled semi-stripping process in which the reduction of the colour'is regulated by the control of the temperature as well as by selection of the proportions of the reagents.

These temperatures and proportions are predetermined by test for each material to produce the particular colour selected out of the range available. Colours not in the available range may be obtained by transforming the darker colour to a lighter colour approximating that desired and then obtaining the exact colour by a slight amount of dyeing.

The stripping agents employed in this process and the proportions in which they are used are selected so that the action proceeds slowly. This facilitates the controlling of the process so that by exact selection of the concentrations of the reagents and of the temperatures a uniform end point can be predetermined for'the production of the desired colour with an. exceedingly level finish.

As the dyes which are to be converted and the materials to be treated vary considerably in their nature, the reagents used and their proportions must be varied. Thus, to treat aniline dyes on fabrics formed of cotton, cotton unions (with wool or silk), or silk. the material is treated in a wooden vat which contains a sheet of perforated zinc, the material being kept out of actual contact with the zinc by a perforated false bottom. Cold water is placed in the vat, before the material is inserted. in sufiicient quantity to cover the material and 1% (one per cent) of sodium bisulphite (Nail-I80 is then added. The material is thoroughly saturated with the solution and is next lifted out of the solution either by rolling it up on a winch to either the first or the second solution,

the function of the coal tar naphtha being to promote the penetration of the treated fabric by the reagent, and the brightening of the shade of the dye under conversion. This second solution is then added to the first solution in the vat in the proportion of about 1 gallon of second solution to every 25 gal lens of first solution contained in the vat. The temperature is then raised to approximately 60 C. and the fabric is then returned. to the vat'and kept in motion. The liquor in the vat is then raised gradually to the particular temperature which has been determined beforehand, by testing, to correspond in the particular colour desired. In this testing a small piece of the material is treated by equivalent processes in the laboratory under conditions estimated to be correct, and, if the desired colour is not produced, the conditions are modified to the necessary extent as determined by further trial and the whole fabric is then treated under the conditions thus determined. The stopping of the process sharply at the desired end point with a level colour is facilitated in a remarkable degree b the addition of about 2% (two percent) of 30% (thirty per cent) acetic acid or 5% cial solution of sodium bisulphate. This step is a safeguard which enables the action to be stopped at the correct end point even (live per cent) of commer- 9o if the control of the process is otherwise carelessly effected. The material isthenv .washed out thoroughly in a 5% I claim: dyed fabric down to any preselected point 1. A rocess of lightening the colour of a on the available range of colour consisting dyed fa bric down to any reselected point in subjecting the fabric to an incomplete on the available range of 00 our consisting in stripping process, controlling the stripping 6 subjecting the fabric to a uniformly and process by regulating the concentration an 1 selectively controlled semi-stripping process temperature of the stripping liquor, and with water containing the products of the finally fixing the resultant colour by addireaction of sodium bisulphite with zinc, with tion of a fixing reagent. the addition of coal tar naphtha. In testimon whereof I aflix my signature. 10 2. A process of lightening the colour of a GEO GE FREEMAN LLOYD. 

